The invention relates to a valve arrangement for pipe lines or containers.
Valves as shut-off members for liquid and gaseous media are required in many technical areas. Depending on the given requirements, different types of valves are utilized in manifold manner. Valves close off or open pipe lines or openings on containers. Valves close off or open, for example, lines between pumps, containers, measuring apparatus and other structural parts. They permit the intake or throughflow or the shutting down of liquids or gases or they can also serve as a sluice for solid bodies. The applications of valves are highly manifold and therewith also the requirements made of their construction. Important parts of a valve are the housing and a movable plate or a valve plate, possibly with a seal, which, depending on the position, enables or shuts down passage. The valve plate is moved from the outside, the atmosphere side, and is intended to close the passage opening depending on its position. In many cases intermediate positions can also be set, with the conductance being changed thereby and the valve in such a case can also be operated as a choke member with adjustable conductance. As a rule, in the closed position a high degree of tightness is demanded and in this case the valve must either be provided with a seal on the housing and/or on the valve plate margin. Here, as a rule, elastomer seals are utilized. Conventionally, one significant requirement made of the valve is that in the opened state as large a cross section is enabled for the passage of the medium. Consequently, a high conductance is to be attained in order to keep the flow losses low. This requires special valve constructions in order to keep the valve size within an acceptable range. A valve can per se be built and utilized with a larger cross section than the line cross sections it serves. For reasons of economy, however, the valve should not be too large, yet, it should nevertheless attain as good a conductance as possible.
A known valve arrangement which is intended to accommodate such demands, is the so-called butterfly valve. This valve type is per se structured simply. Within a tubular section or an annular housing part is disposed a disk-shaped valve plate with a shaft rotatably supported about a central axis. By rotating the shaft outside of the housing, on the atmosphere side, using a drive or manually about approximately 90°, the valve plate for the closing is rotated against the housing part or, for opening, is set into the direction of flow. For good sealing, the housing part is provided at the inner circumference with an elastomer material as a seal. The elastomer material is in many cases not disposed on the housing part but rather on the outer margin of the valve plate encompassing the latter. During the closing movement the seal in this case is squeezed under friction between the inner housing wall and the valve plate margin. Such a valve is described, for example, in DE 33 02 159 A1.
This valve type can be applied in many cases, in particular with liquid media which decrease the abrasion of the friction seal through the lubrication effect or also when lubricants can be utilized and a certain contamination thereby and by particles from the abrasion can be tolerated.
In application cases in which especially high purity is required, such a valve arrangement cannot be utilized. This is in particular the case in vacuum applications in which often highly pure processes are demanded, such as for example in many vacuum surface treatment processes, such as for example in thin-film technology. In such processes a seal would have to be run as a dry seal, since, for example, the use of any type of lubricant must be avoided as much as possible. Even if minimal quantities of lubricants are used, these would be stripped off after a few valve actuations. The seal would be strongly chafed through the friction and the generated particles would impermissibly contaminate the process. There is also the risk that the seal, for example an O-ring, becomes twisted or rolls or is even peeled off. The valve would thereby become non-usable after a short time. The driving forces would also be non-uniform and would change over time; they would, in particular, increase. The fundamental structure of the butterfly valve would per se be highly suitable for the application under vacuum conditions with respect to the good conductance properties attainable with this valve type. Attempts have therefore repeatedly been made to modify this valve type with respect to structure to the effect that the above listed problems can be decreased or avoided.
The known proposals for avoiding the frictional seal are to the effect that with an additional complex mechanism, the valve plate is first raised from the seat and only when the seal no longer touches it, is the plate rotated or, in reverse sequence, during the closing. Such complex valve arrangements have been described, for example, in DE 35 08 318 C1, DE 35 33 937 C1, U.S. Pat. Nos. 3,065,950 and 6,494,434.